The broad objective of this project is to provide a theoretical framework that leads punishment conceptions and research in new directions. Most of what is known about punishment concerns changes in response rate. Because response rate has been virtually the exclusive dependent variable in punishment studies, and it must decrease by definition, typically there is no way to determine punishment mechanisms; they must be inferred. In the proposed project, however, several measures will be obtained (e.g., response rate, response force, response duration, and heart rate), which will provide a unique opportunity to assess punishment mechanisms, and develop new punishment definitions. The specific aim of the proposed project is to test the proposition that punishment effects can be partly explained by somatic slowdown produced by unavoidable aversive stimulation (operationally defined as reduced response and heart rate plus increased response duration). There will be four main tests: 1) do both biologically-relevant and conditioned punishes (e.g., electric shock and response cost, respectively) produce somatic slowdown?, 2) do other procedures that reduce response rate not produce somatic slowdown?, 3) do unavoidable aversive stimuli produce somatic slowdown?, and 4) do avoidable aversive stimuli not produce somatic slowdown? These manipulations will provide the first test of my somatic slowdown theory with rigorous convergent and discriminant validity logical assessments. In addition to testing the somatic slowdown proposition, the proposed experiments also will produce important theoretical and practical information concerning the operant and physiological effects of electric-shock used as a punisher, avoidable aversive stimulus, and unavoidable aversive stimulus. Overall, the project offers many theoretical and empirical possibilities, and the somatic slowdown framework could have a major impact on punishment conceptions, theory, and research.